| Diketopyrrolopyrroles (DPPs) are an interesting class of organic molecule for several reasons; they posses strong visible absorption and are frequently encountered as commercial pigments or dyes, they have a tendency to pack into regular crystal structures, it is easy to functionalize them with different soluble side chains and aromatic groups and they have desirable electronic levels for use in various applications such as transistors, light emitting diodes, and solar cells. In this work, we explore the effect of chemical structures on material properties. By appending different combinations of aromatic groups to a DPP core, the optical and electronic properties can be controlled to give materials with different band gaps, energy levels and charge carrier mobilities. By appending linear alkyl chains of different length and branching, we find that the solid-state ordering and morphology can be changed as well as the degree of crystallinity. Furthermore, this class of material works effectively as active materials in field effect transistors, exhibiting good charge carrier mobilities, and in some cases, ambipolar charge transport characteristics. |
